The present invention relates generally to an open-end (OE) spinning device and, more particularly, to a fiber guide conduit for such a spinning device having a wall surface with an elevated coefficient of friction.
Open-end spinning devices with a fiber guide conduit designed in such manner are described, e.g., in German Utility Model DE-GM 92 18 361.
As is known, during open-end spinning a sliver stored in spinning cans is separated by a so-called opening cylinder into its individual fibers and the latter are fed pneumatically via a fiber guide conduit onto the sliding surface of a spinning rotor rotating at a high speed in a rotor housing.
The yarn qualities which can be achieved also depend, among other things, on how many of the individual fibers are drawn into alignment with one another while they are being fed onto the sliding surface of the spinning rotor and how many of these fibers pass in relative alignment into the rotor groove. The fiber guide conduit of such OE spinning devices is therefore customarily constructed in such a manner that during the fiber transport an acceleration of the flow of transport air takes place, which results in a drawing or elongation of the individual fibers floating in the air flow.
However, both the rate at which the individual fibers enter into the fiber guide conduit as well as the maximum exit rate at which the individual fibers should leave the fiber guide conduit are very largely preset in open-end spinning devices by certain physical structural conditions of such spinning devices and/or by necessities of spinning technology.
The entering rate of the individual fibers into the fiber guide conduit results, e.g., from the circumferential speed of the opening-cylinder fittings. This rotational speed should not drop below a certain value, in the interest of good fiber individualization and of a sufficient cleaning of the feed sliver. If the rotational speeds of the opening-cylinder fittings are too high, however, there is the danger that fiber damage will occur or that undesired separations of so-called material fibers will occur in the area of the soil exit opening.
The maximum exit rate of the individual fibers out of the fiber guide conduit is limited by the rotational speed of the point where the fiber strikes the sliding surface of the spinning rotor. In order to avoid that individual fibers are compressed or buckled when striking a sliding surface which is running rather slowly, it must be assured that the feed rate of the individual fibers is at least not above the rotational speed of their striking point on the sliding surface of the spinning rotor.
In German Utility Model DE-GM 92 18 361 the individual fibers slide over a type of fiber braking surface before they are fed onto the sliding surface of the spinning rotor. That is, this known open-end spinning device comprises a fiber guide conduit whose mouth area has been roughened by sandblasting so that a braking surface is provided for the individual fibers exiting from the fiber guide conduit. This fiber braking surface is intended to cause the individual fibers exiting from the fiber guide conduit, which first pass with their leading end into the effective range of an air flow circulating with the spinning rotor and are subjected thereby to an acceleration, to be mechanically delayed at the same time at their trailing end by the braking surface and elongated as a result.
However, practical experiments have shown that such a sandblast-roughened braking surface does not lead to the improved fiber values hoped for in the area of the mouth of the fiber guide conduit, but on the contrary presents a number of problems.
Specifically, in some instances, individual fibers can remain hanging on the roughened braking surface, where they soon form fiber bundles which result in yarn errors and/or yarn breaks during the following separation. Moreover, a part of the individual fibers first strike the braking surface with their leading end. These fibers then tumble over as a rule and are fed in a totally undefined disposition onto the sliding surface of the spinning rotor.